Count HTTP request error codes with prometheus

cmd/app/serve.go

@@ -199,7 +199,7 @@ func runServeCmd(cmd *cobra.Command, args []string) {
 
 		// Instrument Prometheus metrics
 		handler = promhttp.InstrumentHandlerDuration(api.MetricLatency, handler)
-
+		handler = promhttp.InstrumentHandlerCounter(api.RequestsCount, handler)
 		// Limit request size
 		handler = api.WithMaxBytes(handler, 1<<22) // 4MiB
 	}

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/PaesslerAG/jsonpath v0.1.1
 	github.com/ThalesIgnite/crypto11 v1.2.5
 	github.com/coreos/go-oidc/v3 v3.1.0
+	github.com/felixge/httpsnoop v1.0.2
 	github.com/fsnotify/fsnotify v1.5.1
 	github.com/go-chi/chi v4.1.2+incompatible
 	github.com/google/go-cmp v0.5.7

go.sum

@@ -351,6 +351,8 @@ github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5Kwzbycv
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
 github.com/fatih/structs v1.1.0/go.mod h1:9NiDSp5zOcgEDl+j00MP/WkGVPOlPRLejGD8Ga6PJ7M=
+github.com/felixge/httpsnoop v1.0.2 h1:+nS9g82KMXccJ/wp0zyRW9ZBHFETmMGtkk+2CTTrW4o=
+github.com/felixge/httpsnoop v1.0.2/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/flynn/go-docopt v0.0.0-20140912013429-f6dd2ebbb31e/go.mod h1:HyVoz1Mz5Co8TFO8EupIdlcpwShBmY98dkT2xeHkvEI=
 github.com/form3tech-oss/jwt-go v3.2.2+incompatible/go.mod h1:pbq4aXjuKjdthFRnoDwaVPLA+WlJuPGy+QneDUgJi2k=
 github.com/frankban/quicktest v1.10.0/go.mod h1:ui7WezCLWMWxVWr1GETZY3smRy0G4KWq9vcPtJmFl7Y=

pkg/api/metrics.go

@@ -30,4 +30,9 @@ var (
 		Name: "fulcio_api_latency",
 		Help: "API Latency on calls",
 	}, []string{"code", "method"})
+
+	RequestsCount = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "http_requests_total",
+		Help: "Count all HTTP requests",
+	}, []string{"code", "method"})
 )